100% Visibility at MHz Speed: Efficient Soft Scan-Chain Insertion on AMD/Xilinx FPGAs

• Published in: Applied Reconfigurable Computing. Architectures, Tools, and Applications pp. 1 - 16
• Main Authors: Omidian, Hossein, Hung, Eddie, Gaitonde, Dinesh
• Format: Book Chapter
• Language: English
• Published: Cham Springer Nature Switzerland 27.10.2022
• Series: Lecture Notes in Computer Science
• Subjects: Debug; Emulation; Prototyping; Readback; Scan chain
• ISBN: 9783031199820; 3031199820
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-031-19983-7_1

FPGA-based prototyping has become an increasingly important part of the overall integrated circuit design and verification flow, providing the ability to test an integrated circuit running at (near) speed with realistic inputs and outputs. The reconfigurable aspect of FPGA technology makes them suitable for hardware emulation and prototyping, plus their nature of having over-provisioned resources — inherently necessary to support the late-binding of a wide range of applications — allows support for ‘out-of-band’ functionality such as debug. It is imperative that as much visibility into the inner state of the circuit is accessible in order for debugging to be effective. Full visibility for functional debug can be achieved by building a soft scan-chain out of LUTs and flip-flops, or by using hardened device readback capabilities that use the configuration network to exfiltrate circuit state. In this paper, we show how soft scan-chains can be efficiently and intelligently inserted to give 100% visibility into all user flip-flops of a design and demonstrate how performing parallel scan dumps can be more than 10x faster (reaching 1 MHz) than hardened readback when evaluated on industrial emulation designs in excess of 200K flip-flops.